This invention relates to a service vehicle having a lateral travel system which can be switched to a lateral travel mode.
Conventionally, service vehicles having a lateral travel system have primarily been found among large size conveyance vehicles and some loaders, and reach style electric vehicles as forklifts. In addition, there exists a side forklift with a mast and forks installed sideways in relation to the movement direction of the vehicle to allow the vehicle to handle elongated objects. However, there are no counter balance type forklifts that can move sideways and function like a side forklift in addition to such tasks as generally required. To realize this type of forklift, the front wheels or driving wheels are required to be steerable sideways.
Therefore, a conventional forklift 1, shown in FIG. 5, has right and left front wheels 3 (driving wheels) in a front part of a vehicle body 2, right and left rear wheels 4 in a rear part of the vehicle body 2, and a driver""s compartment 5 on an upper front part of the vehicle body 2. A mast 6 capable of vertically extending and retracting is located at a front end of the vehicle body 2 to be able to tilt in a front-and-rear direction through a front wheel axle 7 extending in a vehicle width direction. Additionally, tilt cylinders 8 enabling the mast 6 to tilt forward and backward are placed between the vehicle body 2 and the mast 6.
The mast 6 comprises a pair of right and left outer frames 9 and a pair of right and left inner frames 10 capable of vertical movement by being guided by the outer frames 9 Disposed between the outer frames 9 and the inner frames 10 is a lift cylinder 11. Additionally, lift brackets 12 capable of vertical movement by being guided on the inner frames 10 are provided, and a pair of right and left forks 13 are secured to the lift brackets 12 through a pair of upper and lower finger bars.
The above mentioned driver""s compartment 5 includes a seat 15, a steering wheel 16 located in front of the seat 15, and a headguard 19 disposed thereabove through front pipes 17 and rear pipes 18 which are erected on the vehicle body 2. A counterweight 20 is located in the rear of the seat 15 on the vehicle-body 2.
However, since the right and left front wheels 3 are driven in common by a same travel drive system, the above mentioned conventional forklift 1 cannot effect straight-sideways steering of the front wheels, thus being unable to move laterally.
It is an object of the present invention is to provide a service vehicle with a lateral travel system, in which driving front wheels can be steered straight sideways and a driving unit can be readily assembled and arranged compact.
To achieve this object, a service vehicle with a lateral travel system according to the present invention comprises right and left front wheels and right and left rear wheels mounted to a vehicle body, respectively to be capable of steering by 90 degrees, each of the pair of right and left front wheels being connected, through an electric drive motor, to a turning member capable of rotating around a vertical axis on the vehicle body, wherein each electric drive motor has an external casing integrally formed with the turning member, which external casing is configured to allow a rotor and a drive shaft to freely rotate therein, the rotor and drive shaft being connected to the front wheel, and means for rotating the turning member is provided.
According to the above mentioned configuration, the electric motor can be assembled with the turning member by inserting, from an outward position on a non-load side, the rotor and the drive shaft into the external casing which is integrally formed with the turning member, with other to-be-fixed parts having been fixed inside the casing. Afterwards, a loaded end of the drive shaft can be connected to the front wheel on each right and left sides. Since the outer casing of the electric motor is thus integrally formed with the turning member and is designed such that the rotor and the drive shaft can freely rotate therein, and this drive shaft is connected to the front wheel, the electric motor can be readily assembled and arranged to be compact in size.
During normal travel, both the right and left front wheels and right and left rear wheels are steered either forward or backward. When switching from a normal travel mode to a lateral travel mode, the rotating means is first activated to turn the turning members around the vertical axes, so that the front wheels can be steered by 90 degrees (straight sideways) in relation to the vehicle body. The front wheels, which are integral with each electric motor, can be steered by 90 degrees both easily and smoothly. After having steered the front wheels or the driving wheels straight sideways, the front wheels are driven in either of to-and-fro directions thereof by the electric motor, whereby the service vehicle can travel laterally either to the right or the left with respect of the vehicle body. At this time, the rear wheels are allowed for follow-up steering by means of a turning castor system or can be forcedly steered following the front wheels.
According to a preferred embodiment of the present invention, a mast is disposed at the front end of the vehicle body and forks are secured to the mast.
According to this embodiment, during a normal travel, both the right and left front wheels and the right and left rear wheels are steered in a front-and-rear direction. A lift lever is then used to raise or lower the forks along the mast to accomplish expected fork operations. This method allows the service vehicle, in addition to normal fork operations, to travel laterally by steering the driving front wheels straight sideways, for example, to readily transport elongated objects using the forks.